The proposed research explores infants' perception of audible and visible events. Three studies will investigate the development of infants' sensitivity to audio-visual relations of 3 levels of specificity. These relations include 1) temporal macrostructure, in this case, the synchrony between sights and sounds of an object's impact, 2) temporal microstructure, here, audio-visual relations specifying the impact of a single object versus a group of objects, and 3) specific object-sound pairings, the relation between modality specific characteristics of a moving object and its impact sound. The research addresses the following questions: What is the nature and basis of the developmental course of audio-visual event perception? What is the developmental progression of infants' detection of the above audio-visual relations? What audio-visual relations do infants abstract from visual and acoustic exploration of an event? Prior studies of intermodal perception have generally tested infants of only one age group and thus have not investigated the nature and course of this developmental process. The proposed research addresses these questions by testing infants of 3 age groups (1 1/2-3 1/2 months) in 3 kinds of tests measuring detection of the audio-visual relations listed above. A new method of assessing intermodal capabilities in young infants is developed and used in the proposed research. The method involves training infants with single films and natural soundtracks of events. Then tests are administered to measure the nature of the audio-visual relations detected through training. In the tests, trials of 2 films and 1 soundtrack are presented. Infants' visual fixation to the 2 films will be recorded to determine whether a preference for the sound specified film is evident as a result of training. The research will test a set of theoretical predictions generated from a Gibsonian invariant detection model of perceptual development; that audio-visual relations are differentiated in order of increasing specificity. These studies can provide the basis for normative data on the development of intermodal perception, and may be used for diagnosing abnormal patterns of development.